1. Field of the Invention
The present invention relates to a recording and playback system for a video cassette recorder (hereinafter "VCR"), wherein a code is recorded in the tape during recording and then the normal playback can be performed only when the code is decoded in reproducing and more particularly, to a recording and playback system for code recording of a VCR in which a control pulse is transformed by the code and recorded in the tape so that the tape is impossible to be reproduced by a general VCR.
2. Description of the Prior Art
FIG. 3 is a block diagram of a recording and playback system of a conventional VCR. As shown in FIG. 3, such system includes a video signal input terminal VI connected through a synchronous separator 1 and an 1/2 frequency demultiplier 2 to a recording terminal a.sub.1 of a recording and playback changing switch SW.sub.1, a control head 8 connected to a movable terminal of a recording and playback changing switch SW.sub.1, a recording terminal a.sub.1 of the recording and playback changing switch SW.sub.2 connected through a control pulse amplifier 5 to a recording terminal b of the recording and playback switch SW.sub.1, a movable terminal of the recording and playback changing switch SW.sub.1 connected to a control pulse input terminal co of a microcomputer 3, an input terminal of a comparator 4 and a recording terminal a.sub.2 of the switch SW.sub.2, a key matrix 6 having a various functional switches SW.sub.3 -SW.sub.5 connected to an input terminals I.sub.1 -I.sub.4. of the microcomputer 3, and an output terminal of the comparator 4 connected to an input terminal of a control circuit 7, wherein the recording and playback changing switches SW.sub.1 and SW.sub.2 are short-circuited to the recording and playback terminals a.sub.1 and a.sub.2 in case of recording, and also, are short-circuited to the playback terminals b.sub.1 and b.sub.2 in case of reproducing, respectively. Therefore, the recording and playback changing switches SW.sub.1 and SW.sub.2 are respectively short-circuited to their recording terminals a.sub.1 and a.sub.2 upon recording, wherein a synchronizing signal of a video signal inputted to the input terminal VI of the video signal is separated from the synchronous separator 1 and then is 1/2 frequency demultiplied at the 1/2 frequency demultiplier 2 thereby being outputted as a control pulse of 30 Hz. The control pulse of 30 Hz is applied through the recording and playback changing switches SW.sub.1 and SW.sub.2 to the control head 8 and is recorded, wherein the control pulse of 30 Hz passed through the recording and playback changing switch SW.sub.1 is applied to the control pulse input terminal co of the microcomputer 3 and used as a control signal of time editing and the like, and also the control pulse of 30 Hz is applied to the comparator 4 as a reference signal.
On the other hand, in case of playback, the recording and playback changing switches SW.sub.1 and SW.sub.2 are short-circuited, respectively, to their playback terminals b.sub.1 and b.sub.2, wherein the control pulse of 30 Hz reproduced at the control head 8 is passed through the recording and playback changing switch SW.sub.2 and amplified at a control pulse amplifier 5 and thereafter applied through the recording and playback changing switch SW.sub.1 to the control pulse input terminal co of the microcomputer 3 and to the input terminal of the comparator 4, and accordingly is controlled similar to recording.
In, such a conventional system, since a device capable of recording and decoding the code is not provided, a user cannot record a tape which only the users can reproduce and therefore, security preservation of the tape is difficult.
Furthermore, in other conventional systems, since the system and method for recording the code and decoding the code are complicated, difficulty in practical application is accompanied therewith, and particularly in cases when other people know the code, one disadvantage is that the tape can be normally reproduced utilizing other VCR's having a decoding function.